The Diary can reveal the mum-of-one will be turning on the style this Friday when she joins hundreds of well-turned-out fillies to report on the much-anticipated final of the Arnotts Best Dressed Lady contest.
Grainne was due to go away on holidays this week but found herself with an unexpected hole in her schedule, alongside thousands of other air passengers, when her flight abroad was grounded.
The star, who joined GMTV sports reporter and former tennis champ Dan Lobb to present festival highlights from Cheltenham just a few weeks ago, stressed that her new job had been cleared by her RTE bosses, given that her work on The All Ireland Talent Show had officially finished for the year.
"It's just a stand-alone thing at the moment but we'll see what comes of it," she said at the time. "I've covered the Galway races for RTE a couple of times and I love the craic and the people."
Grainne's newfound success with the British breakfast show sees her following in the footsteps of Lorraine Keane -- who regularly contributed to GMTV prior to the Galwegian swooping in.
News of the Galway beauty's TV gig came on the first day of the annual festival, which saw Blackstairmountain win the big race of the day, The Evening Herald Champion Novice Hurdle.
Spotted enjoying the hospitality at the VIP tent was TG4 weatherman Daithi O Se, who struck it lucky after taking a flutter on Jigalo, the winner of the third race of the day, the Handicap Hurdle.
The delighted media personality explained how he had Galway captain Padraig Joyce to thank for his big win after the footballer gave him the tip during a night out.
Risteard Cooper and his wife Suzanne McMahon, meanwhile, explained how they would be toasting Daithi with a glass of champagne, after they too placed a bet on the winning horse on his advice.
Also celebrating a big win yesterday was Horse Racing Ireland's Tamso Doyle, whose week got off to a flying start when Zest For Life, the horse owned by her husband David Cox's father, raced past the finishing line to win the first race.
In the same race female jockey Nina Carberry beat off stiff competition from Ruby's sister Katie Walsh, reversing their roles after Cheltenham where Katie reigned victorious on Poker de Sivola in the National Hunt Race.
Off the track competition was also fierce among the ladies, as glamorous females battled it out for the coveted Arnotts Best Dressed Lady prize, worth an impressive €20,000.
Stylish judges -- broadcaster Lorraine Keane, designer Peter O'Brien and Arnotts fashion director Deirdre Devaney -- managed to whittle hundreds of attendees down to just one winner, Eibhilin Nic Ghiolla Bhui from Sallins, Co Kildare.
The glamorous software analyst, who scooped a €1,000 Arnotts voucher, wore a straw hat with a black ribbon that she made herself on the day, coupled with a black jacket and dress from LK Bennett and gloves from Heavenly boutique in Clane.
Among the high-profile names in attendance at yesterday's evening meeting were Jimmy Magee, Niall Quinn, Xpose's Karen Koster, Dublin publican Charlie Chawke and Dragons' Den star Gavin Duffy.
Style savvy ladies are expected to come out in force again today when Tipperary model Andrea Roche and her co-judges chose another deserving winner to compete in Friday's big final.
The big race of the day will be the Punchestown Guinness Cold Cup at 5.30pm when all eyes will be on Denman, who is to be ridden by Tony McCoy.